Circulating biomarkers in patients with abdominal aortic aneurysm

Sammanfattning: Abdominal aortic aneurysm (AAA) develops in 3-6% of the population over 65 years and affects mainly men. AAA has a complex etiology involving inflammation, proteolysis, fibrinolysis and coagulation. The general aim of the present thesis was to study the associations between markers of inflammation, proteolysis, fibrinolysis and coagulation with aneurysm size and growth. In paper I associations between markers for these mechanisms and AAA size were evaluated. Patients with AAA had significantly increased levels of several markers (endothelin ET-1, interleukin IL-6, tumour necrosis factor TNF-α, APC-PCI) compared to age matched healthy controls. Correlations existed between aneurysm size, decreased platelet count, increased high sensitive-C-reactive protein, IL-6 and APC-PCI complex levels. In paper II effects of statin treatment were investigated, showing that patients on statins had lower levels of cholesterol, but also of homocysteine, ceruloplasmin, orosomucoid, (matrix metallo-proteinase) MMP-9 and ET-1 in plasma, but higher levels of albumin, and the APC-PCI complex. In paper III relationships between markers of proteolysis, fibrinolysis and coagulation and aneurysm size and growth during follow-up were studied. MMP-2 levels were lower in AAA patients than in healthy controls. Only MMP-2 was related to AAA size. In paper IV relationships between markers of inflammation and endothelial function and aneurysm growth were studied. We confirmed that initial aneurysm diameter is related to yearly AAA growth. Furthermore, age and initial levels of ET-1 were also related to AAA growth during 7 years follow-up. In paper V patterns of systemic biomarkers and their relationship to aneurysm growth during yearly follow-up of patients with AAA were analyzed. Few relationships were demonstrated between the development of mediators and aneurysm growth during annual analysis of this patient material, which was extended compared to the previous analyses. In conclusion, none of the above biomarkers can predict aneurysm growth or replace ultrasound surveillance.